Recently, a nonaqueous electrolyte secondary battery, such as a lithium ion secondary battery, has substituted for a conventional secondary battery, such as lead secondary battery, nickel cadmium secondary battery and nickel hydride secondary battery, and plays the principle role in a small secondary battery for electronics due to its high power density. Then, it is further expected to develop for a motive power secondary battery for automobile, etc., and higher power density is required. Consequently, it has been investigated for highly filling an active material into an electrode, thick-walling of an electrode material mixture, and thin-walling of a separator and a power collector, etc., so that the capacity per cell has been increased.
The nonaqueous electrolyte secondary battery may be used in a cell in mobile phone, etc., and in multiple cells in laptop computer, engine for automobile and the like. When properties (hereinafter referred to as “battery properties”) such as charging capacity and discharging capacity between cells are varied in case of using in multiple cells, and as a result, a part of cells is subject to large charging load and discharging load to cause problems such as dramatically reduced lifetime. Especially, when the porosity of the electrode material mixture is lowered for highly filling an active material, this problem becomes prominent.
To solve such a problem, it is required to measure the battery properties after conditioning a battery by preliminarily repeating discharge and charge and to select uniform batteries.
Patent Document 1 discloses a process for conditioning a battery at high temperature after using specific additives into the battery. By applying the process, it is possible to shorten conditioning time, but it is insufficient to decrease variability in battery properties.
Also, Patent Document 2 discloses a method for preventing swollen electrode and lowered battery properties when leaving the battery at high temperature by increasing adhesiveness between a negative-electrode collector and a negative-electrode material mixture.    [Patent Document 1] The Japanese Unexamined Patent Publication 2001-52757 (the corresponding foreign patent publication: U.S. Pat. No. 6,268,080)    [Patent Document 2] The Japanese Unexamined Patent Publication 2005-25991